1. Field of the Invention
The present invention relates to a setting tool having a sleeve-shaped housing, a piston guide, a piston displaceable in the piston guide, an ignition unit located in the housing and axially displaceable therein, a cartridge chamber arranged between the piston guide and the ignition unit, with the ignition unit having a cartridge chamber bottom for enclosing a propellant in the cartridge chamber and an ignition element for igniting the propellant.
2. Description of the Prior Art
Setting tools of the type described above can be driven by solid fuels in powder form or pellet form. In this setting tool, the setting or drive piston is driven by combustion gases. With the setting piston, fastening elements are driven into constructional components. German Publication DE-19544105A1 discloses an explosive powder charge-operated setting tool in which a piston guide and an ignition unit with a displaceable ignition pin are arranged in the tool housing, with the piston guide and the ignition unit axially movable relative to the housing against a biasing force of damping means supported in the housing. Before start of a setting process, first, a propellant should be enclosed in the cartridge chamber of the setting tool. To this end, upon the setting tool being pressed against a constructional component, the piston guide that carries the cartridge chamber, in which at that point in time an unused cartridge is located, is pressed against the ignition unit. The ignition unit carries the cartridge chamber bottom that closes the cartridge chamber, enclosing the propellant (cartridge) in the cartridge chamber. The ignition of the propellant is effected upon actuation of the ignition pin that projects forward from the ignition unit. The drawback of the known setting tool consists in that because of a comparatively long time the propellant is enclosed in the cartridge chamber, after a prolong operation of the setting tool, the propellant can self-ignite because of heating of the cartridge chamber.
Accordingly, an object of the present invention is to provide a setting tool of the type described above in which the above-discussed drawback is eliminated.